Tango Romeo A320 is correct.
The triangles on related cabin sidewall panels identify the windows
through which the cabin crew can observe the external S/F position
markings in A300/A310.
This to prevent parallax errors if observed from a different window.
For FBW Airbii there is no necessity to visual check the S/F position
- i.e. no procedure - because there is reliable electronic indication. (IPPU)
However the triangles (and S/F markings) are kept for traditional reasons
(crews originating from non FWB Airbii) only.